The present invention relates to a method for beneficiating a fluorspar concentrate. More particularly, the invention relates to a method for beneficiating a fluorspar concentrate containing apatite as a gangue mineral, by a froth flotation process.
Fluorspar ore commonly contains fluorspar (CaF.sub.2), silica, calcite, clay minerals, and, in certain instances appreciable quantitites of the mineral, apatite (Ca.sub.5 (PO.sub.4).sub.3 (F,OH)). In the production of commercial grades of ore, such as acid-grade fluorspar, it is necessary to concentrate the fluorspar and remove substantial quantities of the gangue materials. For instance, specifications for acid-grade fluorspar currently call for about 97% CaF.sub.2 with less than about 1.5% SiO.sub.2 and less than about 0.2%, and sometimes as low as, 0.06% apatite calculated as P.sub.2 O.sub.5.
Conventional concentration techniques, such as gravity concentration and flotation are used to reduce common gangue minerals to acceptable levels. Because of the similar flotation characteristics of fluorspar and apatite, it is difficult to reduce the apatite content of fluorspar concentrates to a tolerable level. Marsh, G. B., U.S. Pat. No. 3,928,019, has disclosed a method for depressing apatite in the flotation of a fluorspar concentrate utilizing, as a depressant, a reagent obtained by mixing a solution containing complexed polyvalent metal cations with an alkali metal silicate to form a hydrosol. Marsh reports that his method is useful for reducing the apatite content to a concentration of about 1.0 wt.% calculated as P.sub.2 O.sub.5 (2.3 wt.% Ca.sub.5 F(PO.sub.4).sub.3).